Apparatus and a Method For Deployment of a Well Intervention Tool String Into a Subsea Well

ABSTRACT

The present invention regards an apparatus and a method for subsea deployment and/or intervention through a wellhead ( 102 ) of a petroleum well ( 112 ). The apparatus comprises a first module ( 101 ) integrated in a portion of a subsea well intervention system assembly ( 102, 103 ) and/or a subsea production system assembly, the first module ( 101 ) comprising an intervention tool bore ( 201 ); a second module ( 301 ) comprising a tubular element ( 302 ) initially housing an intervention tool ( 314 ), wherein the second module ( 301 ) being arranged for sliding into releasable engagement with the intervention tool bore ( 201 ) of the first module ( 101 ), whereupon the intervention tool ( 314 ) is arranged for disengagement from the tubular element ( 302 ) for deployment of the intervention tool ( 314 ) into the wellbore ( 112 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to and is a U.S.National Phase of PCT International Application NumberPCT/N02006/000087, filed on Mar. 8, 2006, which claims priority under 35U.S.C. § 119 to Norwegian Application Number NO 20051257 filed on Mar.11, 2005. The disclosures of the above-referenced applications arehereby expressly incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an apparatus and a method for deployment of awell intervention tool string into a subsea well associated with theproduction of hydrocarbons.

2. Background

Numerous of today's wells related to the production of hydrocarbons aresubsea wells, meaning that significant parts of the production hardwaresuch as wellheads, valve arrangements, instrumentation, control systems,production manifolds and other accessories are located on the seabed.

Subsea field developments are common in the oil industry today. Thisfield development philosophy enables a low capital expense for theinitial field development compared to for example a platform solution.Hence, subsea production systems have enabled the development of smallfields, remote locations, deep water areas and other fields wheretraditional platform solutions have been non-feasible due to high costs.

As they have matured, a significant operational expense problem hasemerged for the subsea fields: Well maintenance/service is veryexpensive compared to platform wells.

Well maintenance and service comprises a range of methods for deployingrelevant tool strings into live wells in order to do work. Traditionalmethods for deploying/intervening relevant tools into live wellscomprise wire line, coil tubing, and snubbing. The downhole tools thatcan be intervened and applied using such methods include perforationguns, zone isolation devices, data recording tools, fluid samplers, arange of mechanical tools and other devices.

Maintenance from a platform involves rigging up the required equipment(for instance wireline or coil tubing) on an appropriate deck space.Hence, the costs of maintenance are limited to renting/acquiring theequipment that is directly related to the operation of interest.

On subsea wells, a drilling rig or an intervention vessel must bemobilised in order to do the same work. Hence, rental costs for therig/vessel comes on top of the cost of renting the intervention service(wireline/coil tubing) itself. This means that maintaining a subsea wellis tremendously more expensive, typically ten times or more, thanmaintaining a platform well.

There has been a large industrial focus on applying tailor-made vessels,typically boats, for the purpose of subsea well intervention. These havea somewhat lower cost than a drilling rig.

For intervention or maintenance operations to be performed on a livewell, lubricator systems are utilised in order to get tools in and outof the well in a controlled manner. Typically, a lubricator systemcomprises the following:

-   -   A tree connector. This is the interface between the wellhead and        the lubricator stack.    -   Valve housings, so-called BOP's (blow out preventers). These        include (gate-shaped) valves, that can cut cable and coil tubing        and thereupon form a seal against the live well, as well as        valves that can close around the cable/coil tubing, without        damaging this, and form a seal against the well pressure.    -   Riser sections. This is simply spacer pipe. The accumulated        length of the riser and BOP determines the length of tool string        that can be intervened into the well in one run.    -   Top seal assembly. In order to run a cable or a coil tubing in        and out of a well environment, a system that seals between the        high-pressurised well environment and the atmospheric (for        surface operations) or seabed pressure (for subsea operations)        conditions on the outside of the lubricator, is needed.        -   For coil tubing operations, so-called stripper rubbers, that            are ring-shaped moulds of an elastomer material, nylon,            Teflon or similar are used. Stripper rubbers are commonly            split in two for mounting purposes and access during the            operation.        -   Annular bags can also be utilised for coil tubing            operations. These are ring-shaped, elastomer-based barrier            systems. Rubber elements are inflated around the coil in            order to create a seal against it. Annular bags are also            commonly used for heavier pipe operations, such as drilling.            A major difference between the stripper rubber and the            annular bag is the latter's ability to seal against            objects/pipe of various diameter.        -   For slick wireline (slickline) analogues to the stripper            rubbers may be used, so-called stuffing boxes, which is a            stack of elastomer packers that seal around the wire.        -   In order to intervene with a braided cable into a well, a            so-called grease injection head (GIH) is required. By means            of long, narrow pipes (flow tubes) and an injection system            using viscous grease, the pressure differential between the            well and the atmosphere is overcome and a braided cable            intervention can be performed.

A lubricator ensures that barrier requirements are complied with duringall stages of the well intervention operation. This means that newbarriers (between the high-pressurised well fluid and the openenvironment) are established before old barriers are removed. As anexample, a typical well intervention operation involves the followingsteps:

-   -   Assembly of the lubricator system and mounting of this onto the        wellhead;    -   Mounting of the tool string inside the lubricator;    -   Closing of the lubricator with the tool string inside of it;    -   Filling the lubricator with a liquid, for example glycol;    -   Pressure testing the lubricator (upon doing this a new barrier        has been established and verified);    -   Alignment of the lubricator pressure to equal the wellhead        pressure;    -   Opening of the wellhead valves (i.e. the original barrier is        removed);    -   Intervene the tool string into the well to do the required        operation;

When bringing tools out of the well, reversed procedures similar to theone above are used to ensure that the original barriers (the wellheadvalves) are re-established (closed) before opening the lubricator totake out/replace the tool string.

In relation to the development of subsea intervention vessels (boats),associated subsea lubricator assemblies are developed.

As of current, such subsea lubricator systems have been analogues tolubricator systems for surface/platform operations, as described in theprevious section. Hence, a subsea lubricator system, common of today, issimply a “marinated” surface lubricator system, by means of addingfeatures that compensate for the fact that there is a marine environmenton the outside of the lubricator rather that atmospheric air.

Subsea lubricators as of today are limited by several factors.

There are height limitations in that the lubricator can not exceed acertain height. This is related to technical as well as economicalconsiderations. For instance, increasing height means increasing bendingmomentum at the base of the subsea stack where the lubricator isanchored to the subsea wellhead. The latter has been a significantchallenge and limitation with today's lubricators. Also, should thelubricator become too high, big and bulky, this would impose additionalrequirements to the vessel, which again could make the operation exceedaccepted economical limits.

The height restriction imposes direct limitations to tool string length.With current subsea lubricator systems and methods, the wellhead valvescan not be opened prior to having connected, closed, performed fluiddisplacement, and pressure tested the lubricator itself. Hence, thecurrent lubricator technology becomes the limiting factor with respectto tool string length. This again means that operations requiring longtool strings must be performed in several smaller steps. Such steps maydrag the operation out in time and increase the costs dramatically. Inworst case, operations are not initiated as they become non-economical.

As of today, the length of tool string that can be intervened in one runis limited to approximately 20 metres.

There exist lubricator concepts that apply telescopic joints in order tolengthen the lubricator. Typically, such telescopic joints are elongateddownwards through the open wellhead, hence a lengthening of lubricatorspace by a factor close to 100%, compared to standard subsea lubricatorsystems, can be achieved.

For platform operations, there exists a deployment system that allows atool string to be deployed through an open wellhead, and where thedownhole safety valve (DHSV) is the only barrier when bringing tools inand out of the top section of the well. The aim with this technology hasbeen to:

-   -   Run (very) long tool strings into a live well    -   Reduce the height of the traditional lubricator stack    -   Enable operations in wellhead areas with height restrictions

When using this technology, pressure is bled down above a closed downhole safety valve, DHSV, and the tools are brought into the well througha “wide open wellhead”. Upon getting the tools in place, the top sealassembly (for example a grease injection head) is mounted on top of thelubricator stack, before the DHSV is opened and the tools are run to thelower sections of the well to do the work.

Here the lubricator stack and its functions are not removed, but theriser section is, and thereby the main component that contributes toheight. By means of system features that guarantee that no object canfall into the well and damage the DHSV during rig-up, it is allowed tooperate against only one barrier in certain stages of the operation.

Such platform deployment systems are not applicable on subsea wells asthey cannot handle the pollution problematic: Well fluids that arepresent above the downhole safety valve would tend to segregate upwardsand pollute the sea because the well fluids are lighter than the seawater.

SUMMARY OF THE INVENTION

The invention has as its object to remedy, or at least reduce, one ormore drawbacks of the prior art.

The objects is realized through features which are specified in thedescription below and in the following Claims.

It is an object of the present invention to provide an apparatus forsubsea intervention that reduce costs and operational complexity.

A further object of the present invention is to provide a method forutilising the apparatus according to the invention.

The invention aims at reducing lubricator height and, at the same time,dramatically increasing the length of tool string that can be intervenedin one operational step.

The invention comprises a subsea deployment system and a method forconducting intervention. The subsea deployment system comprises two mainmodules, a first module that attaches to the subsea wellhead and/orlubricator assembly, and a second module that attaches to the toolstring to be intervened. More specifically, the first module of theinvention comprises a subsea deployment lubricator module hereinafterdenoted as “SDLM”, which is a system component, or stack of systemcomponents, that forms part of a subsea lubricator. The second module ofthe invention comprises a subsea deployment intervention modulehereinafter denoted as “SDIM” which attaches to the tool string to beintervened. The two system modules interface and interact in a mannerthat enables deployment of long tool strings into wells, with a minimalheight subsea lubricator stack.

The main consequential differences between the invention and existingsubsea lubricator systems are:

-   -   Eliminate/reduced need for riser joints in the lubricator        section, as the tool string is deployed “through the open subsea        wellhead” by means of a unique subsea deployment technique.    -   Capability to deploy almost unlimited length of tool strings in        one run (the upper theoretical limit is given by the distance        from the wellhead to the downhole safety valve).

The main difference from deployment systems for surface/platformapplications is a set of novel system components and techniques thatensure a seal to be present between the well and the outer environment(the sea) during deployment, hence well fluids cannot escape during thedeployment operation.

The SDLM is the “lubricator part” of the subsea deployment system. Inone embodiment of the invention, the lower end of the SDLM is attachedto the wellhead and the upper end attached to a BOP (Blow Out Preventer)module. In another embodiment of the invention, the lower end of theSDLM is attached to the wellhead indirectly, by means of an interfacemodule, a LRP (Lower Riser Package) or other similar equipment.

The SDLM comprises a main bore, preferably provided in the centreregion, and normally of similar or larger inner diameter than thewellbore itself.

The SDLM comprises a seal arrangement. In one aspect of the inventionthe seal is a dynamic seal. In one embodiment, this is a stripper rubbermade of elastomer, nylon, Teflon or similar material. By applying radialor axial forces, the seal arrangement according to said aspect is forcedradial inwards to seal around any matching object that is inserted inthe bore of the SDLM. In another embodiment of the invention, the sealarrangement is an annular bag or similar system that inflates aroundobjects in the centre of the SDLM.

In one embodiment of the invention, the seal arrangement comprises oneof said two sealing elements. In another embodiment of the invention,the seal arrangement comprises a stack of multiple amounts and/or typesof sealing elements. In one embodiment of the invention, some of theseals in a stack serve the purpose as a well barrier, whereas otherserves the purpose as “vipers” in order to prevent pollution to the sea.In one embodiment of the invention, only the “vipers” are fully activeduring normal operation, whereas the other sealing arrangements areactivated in the case of emergency.

The SDLM also comprises a valve assembly. This serves the purpose toprevent upward segregating fluids from the well to pollute the marineenvironment in parts of the operational sequence. Also, the valveassembly serves the purpose of providing a barrier against the wellduring certain operational stages, and to provide means for pressuretesting against, in order to verify seal integrity.

In a preferred embodiment of the invention, the valve assembly includesa double set of flapper type valves, where the upper is a tri-armflapper and the lower is a conventional flapper valve. In one embodimentof the invention, the upper tri-arm flapper valve opens by means offorcing the intervention string assembly into it whereupon the lowerflapper automatically opens as the two valves are mechanically hinged.Hence, the lower valve may be able to contain elastomer seals, sealingsurfaces and other features that should not be exposed to mechanicalcontact with the intervention string. In summary, for this embodiment,the upper tri-arm flapper is to be considered a mechanical activationmechanism for the lower flapper that is the real barrier/sealingmechanism towards the wellbore. In one embodiment of the invention, thevalve/valve assembly is spring-loaded and biases towards a closedposition. In this case, should the intervention string be retrieved outof the valve assembly, the valves will automatically close.

In one embodiment of the invention, the above described valves arecomplemented with another valve, typically a ball- or a gate valve,located below the other valves. This valve enables pressure testing ofseal integrity at the time of stinging the tool string assembly into theSDLM. In another embodiment of the invention, this latter valve fullyreplaces the need for one or both of the described flapper valves and isthe only valve that is required for the described purposes.

In other embodiments of the invention, the valve assembly includes orcomprises alternative valve types, such as ball valves, gate valves andother valves as well as a combination of such type valves. These valvescould be operated mechanically, electrically, hydraulically or by meansof other relevant forces, using intervention tools or surface operatedelectrical, hydraulic or other surface operation mechanisms connected tothe subsea mounted equipment. Also, wireless activation signals could beapplied to activate the valves.

In one embodiment of the invention, the SDLM comprises an anti-blowoutsystem. In one embodiment of the invention, this is a device that ispre-installed and is centered in the bore of the SDLM, an anti-blowoutsub, which attaches to the intervention string assembly duringdeployment. The anti-blowout sub has an OD that is larger than the ID ofthe SDLM above the hang-off point of the anti-blowout sub. Hence, theintervention string can not be blown out of the well.

In one embodiment of the invention, the anti-blowout sub and thematching anti-blowout profile in the SDLM have the shape andcharacteristics of a dampener. In one embodiment of the invention, thetwo components form the male and female of a hydraulic dampener, wherefluid becomes trapped between the anti-blowout sub and the anti-blowoutprofile of the SDLM, and the said fluid only can escape via narrowchannels that reduce in size or number the more fluid that is displaced.Hence, a gradual dampening pattern is achieved in order to avoid systemdamage due to hard impacts between the anti-blow-out sub and the SDLM.In other embodiments of the invention, the dampener mechanism is basedon other known dampener principles such as springs, friction dampenersand other.

In another embodiment of the invention, the anti-blowout function ishandled by means of a gripping/locking system that prevents upwardmovement of the intervention string assembly. In one embodiment of theinvention, upward movement of the intervention string assembly directlymechanically activates the gripping/locking system. In anotherembodiment of the invention, the gripping/locking system is activated bymeans of sensors detecting unwanted situations (leakage, kick, blowout,unexpected upward movement of the intervention string assembly). Suchsensors could include detection devices for motion, position, pressure,fluid flowrate, fluid composition, volumetric changes and other. In oneembodiment of the invention, the gripping/locking system is operatoractivated. In another embodiment of the invention, the gripping/lockingsystem comprises a combination of some or all of the herein mentionedactivation features.

In one embodiment of the invention, the gripping/locking system includesslips that slide gently along the intervention string assembly whilethis is being deployed into the well, but makes a firm grip at theinstant this starts to move upwards. For deploying out of the well, theslips are foreseen retrieved/removed radial to some distance away fromthe intervention string assembly in order to deploy this out of the well(i.e. upward movement), but linked, in a fail-safe mode, to a releasemechanism that activate the slips and make them grip the interventionstring assembly in case an un-wanted event (e.g. a blowout, a kick orsimilar) should take place. Such an un-wanted event could be indicatedby means of monitoring the speed of the upward movement of theintervention string assembly, the fluid displacement into the wellduring deployment out, acceleration or other indicators of unwantedevents, or a combination of such.

In one embodiment of the invention, the gripping/locking feature isensured by means of operator activation of the annular bag that in oneembodiment forms part of the seal arrangement of the SDLM. Here, theannular bag is not fully inflated against the intervention stringassembly during normal operations, but only so in the case of anemergency.

In a preferred embodiment of the invention, the SDLM comprises flushingsystems in order to remove unwanted fluids from contained spaces beforeopening access to the well, to the open environment, to flowlines orsimilar. In one embodiment of the invention, flushing lines are run andoperated from the vessel used for the subsea intervention operation. Inanother embodiment of the invention, dedicated vessels/tanks and pumpsystems are used for flushing purposes.

In one embodiment of the invention, the SDLM and accessories comprisesdesign and system to avoid fluids being trapped in contained spaces,which can prevent system functionality.

In a preferred embodiment of the invention, the SDLM and accessoriescomprises means for pressure testing and monitoring of such during allrelevant operational stages.

In a preferred embodiment of the invention, the SDLM and accessoriescomprises means for monitoring of operational parameters such aspressure, temperature, fluid flow rate, volume displacement and fluidproperties during all stages of the operation. In a preferred embodimentof the invention, the SDLM comprise a position indicator system thatcorresponds with the intervention string assembly.

In a preferred embodiment of the invention, the SDLM comprises a stoparrangement for preventing further insertion of the intervention stringassembly into the SDLM. Also, the SDLM comprises means for locking partsof the intervention string assembly in place during certain operationalstages.

In one embodiment of the invention, the SDLM comprises access for a killline to be attached, should there occur a need to kill the well. In oneembodiment of the invention, the kill line is run and operated from thevessel used for the subsea intervention operation.

In one embodiment of the invention, the whole or parts of the SDLM isincorporated as a part of a permanent subsea wellhead system. Typically,the valve assemblies could form part of such a permanent system.

The SDIM is a device that, together with the intervention toolsthemselves, forms an intervention string assembly of the subseadeployment system.

The SDIM comprises a tubular element, hereinafter denoted as “flushpipe” and inner seal/latch subs to be mounted on the intervention toolstring of interest. In one embodiment of the intervention, the toolstring is mounted inside the flush pipe with at least one seal/latch subprovided in each endportion of the intervention tool string.

In a preferred embodiment of the invention, the outer surface of theflush pipe is uniform and smooth and forms a seal against the SDLM'sseal arrangement. Hence, when the SDIM is stung into the dynamic seal ofthe SDLM, this forms a seal in the annular space between the well andthe open environment. Preferably, another seal of similar purpose isprovided on the inside of the flush pipe present in the annular spacedefined by the flush pipe and the seal/latch subs attached to the toolstring.

In one embodiment of the invention, in the bottom of the tool string,there is a connector sub for connecting the tool string to theanti-blowout sub of the SDLM. In one embodiment of the invention, theconnector mechanism comprises a standard latch system, such as a GS typelatch. In another embodiment of the invention, the anti-blowout sublatches onto the flush pipe of the SDIM (and not the tool string). Inthis embodiment, the anti-blowout sub is hollow and allows theintervention tool string to be run through it.

In a preferred embodiment of the invention, at least one of theseal/latch subs comprises a latch that attaches the intervention stringto the flush pipe.

In one embodiment of the invention, the flush pipe does not cover partsof the tool string during installation. Typically, this involves caseswhere the tool string can be made of similar uniform shape and outerdiameter as the flush pipe, and/or cases where said non-covered parts ofthe tool string are going to be permanently left in the well, such asfor zone isolation devices. In one embodiment of the invention, theflush pipe is omitted. This would typically apply for cases where theentire tool string can be made of similar uniform shape and outerdiameter as the flush pipe.

In a preferred embodiment of the invention, the flush pipe includes aso-called “no-go profile” in the top portion that matches a similarprofile in the SDLM. This feature physically prevents the flush tubefrom being deployed lower than the no-go profile permits. One intentionwith the no-go feature is to ease exact depth determination. Also, theno-go feature is a very important system feature in case of anemergency. Should there occur a need to drop the SDIM, this will stop ina controlled manner in the no-go profile. Otherwise, a falling SDIMcould drop through the downhole safety valve and create a severesituation. In one embodiment of the invention, the no-go system includesone or more dampening functions to enable a smooth landing of the SDIMinto the SDLM, said functions could be hydraulic-, spring-,friction-based or other damper principles.

In some situations, for example in the case of tool strings of varyingouter diameter and shape, like production logging strings, it might notbe feasible to use solid, large size seal/latch subs. In particular,such seal/latch subs could conflict with the operational scope if placedin the bottom of such tool strings. In one embodiment of the invention,hollow, fluted, expandable or similar feature seal/latch subs are used.In another embodiment of the invention, instead of a seal/latch sub, thebottom and/or other parts of the flush pipe is provided with a valvesystem. This could comprise one or more ball valves, gate valves,flapper valves, or other types and/or combination of valves. Theoperation of the valve system could be by means of a shifting toollocated in the bottom of the tool string, or by means of surfaceoperator controls that are mechanical, hydraulic, electrical,fibre-optical and/or wireless activation based. Remote activationtechniques, such as wireless signals based on acoustic, electromagnetic,pressure pulse or other methods known per se, could be applied toactivate the valve system.

In one embodiment of the invention, the SDIM comprises a system forfluid displacement. Typically, in order to avoid pollution whendeploying out of the hole, this feature could be applied in cases whereit is not possible to obtain a good seal between the flush pipe and theseal/latch subs after the tool string has been in the well.

In a preferred embodiment of the invention, the SDIM comprises passivemodules of a position indicator system. This could be magnets, weakradioactive sources and other types of passive system components knownper se. In another embodiment of the invention, the SDIM comprisesactive position indicator modules.

In the event of loosing the tool string in the well and the flush pipeneeds to be withdrawn from the hole “on its own”, a plug would normallybe run in the bottom of the flush pipe. In a preferred embodiment of theinvention, the bottom section of the flush pipe is compatible withplugs, by means of having necessary reinforcements and/or plug settingprofiles.

In most relevant subsea well intervention cases, the subsea well ofinterest will produce into a manifold that receives flow from a numberof wells. Hence, the manifold will be pressurised during the entiresubsea intervention operation. This prohibits displaced fluids from thedeployment operation to be routed into the manifold. Also, in mostcases, the downhole safety valve (typically a flapper valve) will beclosed and have a significant pressure under it, hence displaced fluidscan not be routed into the well neither. To avoid fluids being trapped,hence preventing the subsea deployment operation from becoming feasible,a volume monitoring and storage module (VMSM) is introduced.

In a preferred embodiment of the invention, the VMSM comprisescomponents for monitoring in- and out-flux of fluids from the well aswell as other relevant data when deploying in and out of the well. Inone embodiment of the invention, the instrumentation of the VMSMincludes sensors for measuring pressure, temperature, flow rate, fluidcomposition, volumetric changes, density and other relevant parametersin order to gain sufficient control of what fluids goes in and out ofthe well during the various operational steps.

In one embodiment of the invention, the VMSM also comprises a system forhandling and/or storing fluids that are displaced and replaced duringthe operational sequences. In one embodiment of the invention, the VMSMcomprises a tank, located at the seabed or at the vessel itself, thatfluids are routed to while deploying into the well and returned fromwhen deploying out of the well.

In another embodiment of the invention, rather than using a tank,available lines that are permanently connected to the well of interest,are used for displacement and replacement of fluids. In one embodimentof the invention, such line could be a so-called “annulus line”.

In one embodiment of the invention, the VMSM comprises a pump systemthat enables displacement of fluids to the production header whiledeploying in, and retrieval of fluids, from the same header or analternative location, when deploying out of the well.

In one embodiment of the invention, a line from a dedicated tank at theseabed or the surface vessel supplies a hydrate inhibitor that is routedinto the wellbore when deploying out of the well. In that way, excessivehandling of wellbore fluids is avoided.

In one embodiment of the invention, access to the wellbore fluid isachieved by mounting the VMSM onto the choke bridge of a subseawellhead. In another embodiment of the invention, the same access isachieved by means of dedicated ports in the SDLM or an alternativelocation on the subsea stack and/or flowline system.

The subsea deployment system according to the present invention willtypically be applied for all subsea well intervention operations. Ingeneral, by means of eliminating or at least reducing the riser of astandard subsea intervention stack as well as providing a mean forintervening very long tool strings in one operational step, the subseadeployment system could be a valuable system component in each and everysubsea intervention operation.

The subsea deployment system enables operations, that otherwise wouldrequire several runs in the hole, to be performed in only one run.Typically, such operations involve deploying long perforation guns,zonal isolation strings or data logging strings.

In the case of a horizontal x-mas tree, a typical subsea deployment andintervention method according to the invention would include thefollowing steps:

-   -   Pull the debris cap off the tree.    -   Mount the SDLM on top of the wellhead or equivalent, using an        appropriate connector sub.    -   Mount the BOP on top of the subsea lubricator module.    -   Pull the tree plugs of the horizontal x-mas tree. A small riser        section on top of the SDLM and BOP might be required to get        sufficient space. Upon pulling the tree plugs, the DHSV and the        SDLM valve assembly forms the remaining barriers.    -   Mount the tool string inside the flush pipe, assembling        component by component, whilst the lower segments are lowered        into the sea. Inside the flush pipe, seal/latch joints are        attached to the top and bottom of the tool string in order to        form seals between the inside of the flush pipe and the outer        environment. Typically, the assembly operation is conducted some        horizontal distance away from the wellhead in case of        accidentally dropped objects.    -   Prior to building the cable head and mounting this on top of the        tool string, the cable is tread through the grease injection        head.    -   When the SDIM is assembled: The vessel is positioned above the        well and the SDIM lowered into the sea with the grease injection        head following closely behind (above), both held by their        respective wires and guiding systems.    -   The bottom of the SDIM/flush pipe is guided into the BOP and the        SDLM. Now, the SDIM forms a seal against the SDLM dynamic seal,        whereupon it latches onto the anti-blowout sub.    -   A pressure test is conducted to confirm seal integrity across        the dynamic seal of the SDLM. For horizontal x-mas trees, this        pressure test is conducted against a valve in the SDLM valve        assembly. For vertical x-mas trees, this pressure test could be        conducted against one of the valves in the tree itself.    -   Sea water that is trapped between the bottom of the SDIM and the        SDLM valve assembly is removed by means of the SDLM flushing        systems. This is done to avoid hydrate and similar problems that        might occur when sea water becomes mixed with well fluids.    -   The anti-blowout sub is released from the SDLM and the SDIM is        continued lowered into the hole.    -   The SDLM valve assembly is opened and the SDIM is lowered        further, until the top of the SDIM is inside the SDLM and the        no-go profiles meet.    -   The SDIM is anchored to the SDLM top section.    -   The grease injection head is lowered on top of and attached to        the BOP. Now, the total “lubricator” is in place.    -   Sea water that is trapped between the top of the SDIM and the        grease injection head is removed by means of the SDLM flushing        systems.    -   The tool string is released from the flush pipe. This can be        achieved by means of applying forces to the wireline cable or        coil tubing, or by means of applying hydraulic, electrical,        mechanical or other forces and/or impulses to the flush pipe        through the wireline, coil tubing or directly from the vessel to        the SDLM itself. Also, wireless communication methods could be        applied for this purpose.    -   The tool string is run to the well section of interest,        whereupon it performs the relevant operation, before it is        retrieved out of the well.    -   The tool string is pulled into the flush pipe and latches onto        the flush pipe's seal/latch sub profiles. The seals in the        seal/latch subs in the top and bottom of the tool string ensures        that pollutants from the well that might have attached to the        tool string are now contained inside the flush pipe while        deploying this out of the well and through open water.    -   Prior to disconnecting the grease injection head (GIH) and        pulling the flush pipe with the tool string out of the BOP, the        volume between the grease injection head and the flush pipe is        flushed with a fluid that replaces all well fluids and other        contaminants. Typically, the replacement fluid is characterised        by being harmless to the environment as well as being of a        hydrate preventive nature.    -   In one embodiment of the invention, the flush pipe and the SDIM        are flushed with a fluid that replaces most of the well fluids        in order to avoid excessive exposure of such on the vessel.    -   The grease injection head (GIH) is loosened from the BOP and        lifted slightly above the rest of the lubricator stack.    -   The SDIM is loosened from the SDLM and retrieved out of the        well.    -   The grease injection head (GIH) is retrieved in the same        operation.    -   Upon having passed the SDLM valve housing the anti-blowout sub        connected to the SDIM lands in the anti-blowout profile of the        SDLM.    -   The SDLM valve assembly is closed.    -   The volume between the SDLM valve assembly and the bottom of the        SDIM is flushed with a fluid that replaces all well fluids and        other contaminants.    -   The SDIM is released from the anti-blowout sub. This can be        achieved by means of applying forces to the wireline cable or        coil tubing, or by means of applying hydraulic, electrical,        mechanical or other forces and/or impulses to the flush pipe        through the wireline, coil tubing or directly from the vessel to        the SDLM itself. Also, wireless communication methods could be        applied for this purpose.    -   The SDIM is pulled out of the lubricator stack, whereupon the        SDIM and the grease injection head are retrieved to the        intervention vessel and disassembled.    -   The x-mas tree plugs are reinstalled and pressure tested.    -   Thereupon the BOP module and the subsea deployment lubricator        module are retrieved.    -   The debris cap is reinstalled and the operation is finished.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows is described a non-limiting exemplary embodiment of apreferred embodiment which is visualized in the following drawings, inwhich:

FIG. 1 shows a simplified illustration of the overall lubricator systemaccording to the present invention as it appears when rigged up at theseabed, with an intervention operation in progress.

FIG. 2 shows in a larger scale and partly in cross section the SubseaDeployment Lubricator Module (SDLM) with schematically illustratedinternal features.

FIG. 3 shows in smaller scale a view of the Subsea DeploymentIntervention Module (SDIM).

FIG. 4 shows partly in cross section a view of the SDIM in FIG. 3 with awireline tool string (perforation gun) mounted inside.

FIG. 5 shows partly in cross section and in smaller scale a view of theSDLM and SDIM in a 1^(st) step in the process of deploying in a wirelinetool string.

FIG. 6 shows partly in cross section a view of the SDLM and SDIM in a2^(nd) step in the process of deploying in a wireline tool string.

FIG. 7 shows partly in cross section a view of the SDLM and SDIM in a3^(rd) step in the process of deploying in a wireline tool string.

FIG. 8 shows partly in cross section a view of the SDLM and SDIM in a4^(th) step in the process of deploying in a wireline tool string

FIG. 9 shows partly in cross section a view of the SDLM and SDIM in a5^(th) step in the process of deploying in a wireline tool string.

DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS

FIG. 1 illustrates the system overview as it appears at the seabed witha wireline intervention in progress. The Subsea Deployment Module (SDLM)101 is attached to the X-mas tree or wellhead 102. Alternatively therecould be a separate module, for example a wellhead connector, betweenthe SDLM 101 and the X-mas tree/wellhead 102, but that is notillustrated here. A BOP (Blow Out Preventer) 103 is provided on top ofthe SDLM 101. A Grease Injection Head (GIH) 104 is provided on top ofthe BOP 103. A wireline cable 105 enters the GIH 104 in a top portion ofthe GIH 104. Inside the illustrated subsea stack, the interventionstring assembly is located. However, this is not shown in FIG. 1. TheVolume Monitoring and Storage Module (VMSM) 107 is connected to theproduction flowline 108. The VMSM comprises a volume tank 109 as well asinstrumentation 110. A kill line 111 to the vessel is shown connected tothe SDLM 101. Below the X-mas tree/wellhead 102, the wellbore 112, i.e.the well itself is illustrated.

FIG. 2 shows in a larger scale and partly in cross section the SDLM 101.This comprises a centre bore 201, a dynamic seal 202, a valve assembly203 and an anti-blowout system 206. The valve assembly 203 comprises anupper, tri-arm flapper valve 204 and a lower, conventional flapper valve205. Also, in this illustration, the anti-blowout system 206 comprisesan anti-blowout sub 207 and a SDLM anti-blowout profile 208. In order toclean the system for unwanted fluids at given operational stages, aflushing system comprising an upper flushing bore 209 and a lowerflushing bore 210 are applied. For illustrative purposes the flushingsystem is only indicated by bores 209, 210 in the SDLM 101. However, aperson skilled in the art will be familiar with such a flushing system.The SDLM 101 also comprises a dynamic seal activation system 212 foroperating (activating/deactivating) the dynamic seal 202 also known to aperson skilled in the art. In the upper portion of the SDLM 101, thereis a SDIM latch 211 arranged for attaching to the intervention stringassembly. Also, a lip or “no-go profile” 213 extending from the surfacein the top portion of the bore 201 of the SDLM 101 is provided forreceiving a corresponding profile of the SDIM 301, thereby preventingfurther deployment of the SDIM 301 in the bore 201 of the SDLM 101. Thekill line 111 to the vessel is also illustrated. Accessories such asaccess lines, pumps, fittings, check valves, seals and similar are notshown. However, such accessories are known to a person skilled in theart.

FIG. 3 shows the SDIM 301 as it appears when assembled. In the upperportion, this module has an outer latch profile 312 and the SDIM no-goprofile 313 as mentioned above. In the bottom, sticking out of the SDIM301, a GS latch 311 is illustrated. The function and purpose of thecomponents herein are explained in connection with FIGS. 5-9. A portionof a wireline cable 105 extending to the surface is also illustrated inthe figures.

FIG. 4 illustrates the internal system components of the SDIM 301. Theflush pipe 302 forms the outer body of the SDIM 301. This is a pipeelement having an outer surface finish that enable the dynamic seal 202of FIG. 2 to provide a seal against it. A wireline tool string 314 ismounted inside the flush pipe 302. Said tool string 314 comprises acable head 303, an upper seal/latch sub 304 with its seal 305 and latch306, the wireline tool 314 itself, in this example a perforation gun307, a bottom seal/latch sub 308 with a seal 309 (no latch included onthis sub) and a GS Latch 311. The GS latch 311 is provided forconnecting the wireline tool string 314 onto the anti-blowout sub 207illustrated in FIG. 2. In the upper end of the flush pipe 302, there isan outer latch profile 312 that allows the flush pipe 302 to be anchoredto the SDLM 101 (cf. FIG. 2—the SDIM latch 211) after installation and aSDIM no-go profile 313 that matches the SDLM no-go profile 213 of FIG.2.

FIG. 5 shows the 1^(st) step in the process of deploying in a wellservice tool string using the Subsea Deployment Module. In the figure,the SDIM 301 is being lowered into the bore 201 of the SDLM 101,whereupon the GS latch 311 attaches to the anti-blowout sub 207.

FIG. 6 shows the 2^(nd) step of the operation. Upon a successfulconnection of the GS latch 311 onto the anti-blowout sub 207, theanti-blowout sub 207 is released from the SDLM 101. The connection andrelease mechanism between the anti-blowout sub 207 and the SDLM 101 isnot shown. However, such a release mechanism is known to a personskilled in the art and could for example, but not limited to, be a latchmechanism operated by applying forces on the wireline wire, or a releasemechanism operated from the vessel or another remote location by meansof hydraulic, electrical or mechanical impulses and/or activationmechanisms, or other known attachment/release mechanisms. Further, theSDIM 301 with the anti-blowout sub 207 is lowered further until itcontacts the tri-arm flapper valve 204. This also forces theconventional flapper valve 205 to open, whereupon the SDIM 301 with theanti-blowout sub 207 is further lowered towards and into the wellbore.

FIG. 7 shows the 3^(rd) step in the process. Here, the SDIM 301 with theanti-blowout sub 207 is further lowered towards and into the wellboreuntil the flush pipe 302 lands inside the SDLM 101. This takes placewhen the SDIM no-go profile 313 has made a physical stop in the SDLMno-go profile 213. Now, the SDIM latch 211 of the SDLM 101 is alignedwith the Outer Latch Profile 312 of the flush pipe 302.

FIG. 8 shows the 4^(th) step of the operation. Here, the SDIM latch 211of the SDLM 101 is activated to attach onto the outer latch profile 312of the flush pipe 302, hence the flush pipe 302 becomes attached to theSDLM 101.

FIG. 9 shows the 5^(th) step in the process. Here, the wireline tool 314is released from the flush pipe 302 by means of releasing latch 306 ofthe upper seal/latch sub 304. When the latch 306 is disconnected, thewireline tool 314 is free to be intervened into the well. Prior toreleasing the latch 306, the Grease Injection Head (GIH, cf. 104 inFIG. 1) is mounted on top of the SDLM 101 in order to ensure that allrequired barriers between the well and the outer environment are inplace prior to the well intervention. In this example, the anti-blowoutsub 207 follows the wireline tool 314 into the well during the wellintervention. In a preferred embodiment of the invention, theanti-blowout sub 207 attaches to the flush pipe 302 directly and doesnot follow the wireline tool 314 into the well. When deploying out ofthe well, the sequence described in FIGS. 5-9 is mainly reversed, withsome minor variations. Flushing to displace unwanted fluids might berequired in one or more steps to avoid pollution to the sea when pullingthe SDIM 301 out of the SDLM 101 after ended operation.

1. An apparatus for subsea deployment and/or intervention through awellhead (102) of a petroleum well (112), characterized in that theapparatus comprises: a first module (101) integrated in a portion of asub-sea well intervention system assembly (102, 103) and/or a subseaproduction system assembly, the first module (101) comprising anintervention tool bore (201); a second module (301) comprising a tubularelement (302) initially housing an intervention tool (314), the secondmodule (301) being arranged for sliding into releasable engagement withthe intervention tool bore (201) of the first module (101), whereuponthe intervention tool (314) is arranged for disengagement from thetubular element (302) for deployment of the intervention tool (314) intothe wellbore (112).
 2. The apparatus according to claim 1, characterizedin that at least one portion of the tool bore (201) is provided with atleast one seal element (202) arranged for sealing an annulus defined bythe tool bore (201) and the second module (301).
 3. The apparatusaccording to claim 2, characterized in that the at least one sealelement is a dynamic seal (202).
 4. The apparatus according to claim 1,characterized in that the second module (301) is provided with a sealarrangement (305, 309) for sealing off an annular space defined by thetubular element (302) and the intervention tool (314).
 5. The apparatusaccording to claim 1, characterized in that a portion of the tool bore(201) of first module (101) comprises a valve assembly (203) which in aclosed position provides a barrier between the well (112) and adownstream portion of said first module (101).
 6. The apparatusaccording to claim 1, characterized in that the second module (301) isprovided with at least one latch device (306, 310) arranged forselectively disengaging the intervention tool (314) from the tubularelement (302).
 7. The apparatus according to claim 1, characterized inthat the first module (101) is provided with a bore (111′) forconnection of a kill line (111).
 8. The apparatus according to any ofthe preceding claims, characterized in that the apparatus is providedwith an anti-blowout device (206).
 9. The apparatus according to claim8, characterized in that the anti-blowout device (206) comprises ananti-blowout sub (207) and an anti-blowout profile (208), said profile(208) being provided within or being an integrated part of a portion ofthe bore (201) of the first module (101), said profile (208) beingarranged downstream of said sub (207), wherein an outside diameter ofsaid sub is larger than the internal diameter of said profile (208). 10.The apparatus according to claim 9, characterized in that the sub (207)is hollow and is arranged to engage with a portion of the tubularelement (302).
 11. The apparatus according to claim 8, characterized inthat the anti-blowout device (206) comprises means arranged for grippingand locking the movement of the second module (301) in the first module(101).
 12. The apparatus according to claim 11, characterized in thatthe anti-blowout device (206) comprises a slips module comprising slipsarranged to glide along the outside of the second module (301) duringdeployment into the well (112) and, if the second module (301) isinstantly moved in an upward direction out of the well (112), isarranged to grip around a portion of the second module (301).
 13. Theapparatus according to any of the preceding claims, characterized inthat the first module (101) is provided with at least one flushingsystem (209, 210) for removing unwanted fluids from contained spacesbefore providing access to the well.
 14. The apparatus according to anyof the preceding claims, characterized in that the first module (101) isprovided with a stop arrangement (213) for engaging a substantiallycorresponding stop arrangement (313) in the second module (301), therebypreventing further insertion of the second module (301) beyond anultimate insertion position of the second module (301) in the bore (201)of the first module (101).
 15. A method for subsea deployment and/orintervention of a petroleum well (112) through a wellhead (102),characterized in that the method comprises the following steps:integrating a first module (101) that comprises an intervention toolbore (201), in a portion of a subsea well intervention system assembly(102, 103) and/or a subsea production system assembly; lowering a secondmodule (301) comprising a tubular element (302) sealingly housing anintervention tool (314) engaged with the tubular element (302) intoengagement with the tool bore (201) of the first module, at least aportion of the annulus defined between the tool bore (201) and thetubular element (302) being sealed; disengaging the intervention tool(314) from the tubular element (302), and running the intervention tool(314) into the wellbore (112).
 16. A method for retrieval and/ordeploying out of an intervention tool (314) through a wellhead (102) ofa subsea petroleum well (112), characterized in that the methodcomprises the following steps: pulling the intervention tool (314) intoengaging connection inside a tubular element (302) of a second module(301), the annulus defined by the tubular element (302) and theintervention tool (314) being sealed at a top portion and a bottomportion of the second module (301), a portion of which being inengagement with and sealingly housed in a tool bore (201) of a firstmodule (101); disengaging the second module (301) sealingly housing theintervention tool (314), and retrieving the second module (301) out ofthe first module (101) through open water and to a surface.
 17. Themethod according to claim 14, characterized in that flushing operationsare executed during the retrieval of the second module (301) from thefirst module (101) in order to avoid any well fluid to communicate intothe environment outside the well.